1. Field of the Invention
The present invention relates to a process for producing a 2-nitrocycloalkanone.
2. Description of Prior Art
2-Nitrocycloalkanone and its derivatives are useful substances in the production of polymers, and particularly in the production of nylon. Heretofore, these materials have been produced by such processes as the nitration of cycloalkenyl acetate with nitric acid; dehydrogenation of 2-nitrocycloalkanol with an oxidizing reagent; reaction of cycloalkenyl acetate with acetyl nitrate; etc. All of these prior art processes, however, required relatively expensive reactants, which were difficult to obtain. Moreover, they suffered from the distinct disadvantage that they resulted in relatively low product yields.
Alicyclic olefins have previously been converted to .alpha.-nitro-ketones in a two-step procedure using nitrogen dioxide (see Lachowicz, et al., "Peroxynitrates," Journal of Organic Chemistry, 32, pp. 3885 (1967)). Further, Lachowicz et al., in U.S. Pat. No. 3,657,349 show the application of a two-step nitrooxidation procedure for the conversion of cycloalkenes to nitrocycloalkanones, in which the cycloalkene is first oxidized by a combination of oxygen and dinitrogen tetroxide to an intermediate peroxy nitrate compound and then denitrated in a second step by a catalyst. However, these prior art procedures require the use of a two-step nitrooxidation procedure, and it would be very attractive industrially to provide a technique for producing 2-nitrocycloalkanones in a single-step procedure.
The disclosure of Pivawer in U.S. Pat. No. 3,806,547 shows such a one-step nitrooxidation procedure of cycloalkenes in which a cycloalkene is nitrooxidized by oxygen and dinitrogen tetroxide in the presence of a denitrating catalyst and a dipolar, aprotic solvent. In the process, large quantities of water must be added to the reaction solution to separate the product. This means that in order to recover the catalyst in an anhydrous state, extra equipment must be used to remove water. The amount of water required to treat the reaction solution is dependent upon the amount of catalyst present. Further, it is important from the industrial economic viewpoint that the amount of catalyst used be reduced to as small amounts as possible.
Therefore, a need continues to exist for a one-step procedure for the nitrooxidation of cycloalkenes in which the product nitrocycloalkanone is obtained in high yields, the amount of catalyst is minimized and the use of water to extract the catalyst from solution is avoided.